Intraductal papillary neoplasm of bile duct with invasive carcinoma as an intrahepatic cystic lesion, with successful preoperative diagnosis.

An 82-year-old man presented to the emergency department with abdominal pain and febrile symptoms that had been present for 4 days. Blood tests showed elevated liver enzymes and white blood cell count, and abdominal contrast-enhanced CT revealed a 35 mm cystic lesion in the left lateral liver lobe. On closer examination, the cystic lesion was found to have contiguous bile duct dilatation and internal nodules. Furthermore, mucus production was observed during endoscopic retrograde cholangiopancreatography, which led to the diagnosis of intraductal papillary neoplasm of the bile duct (IPNB), with cystic infection. Although the patient was an older adult, there was no background disease that would have prevented surgery, and resection was performed. Pathological examination revealed type 1 IPNB, with invasive carcinoma. The number of reports of IPNB is expected to increase with an increasing older population in Asia, and we report the findings of this case.